Apparatus and a method for facilitating the connection of pipes

ABSTRACT

An apparatus for facilitating the connection of pipes which apparatus comprises a rotary ( 1 ) and jaws ( 20, 21, 22 ), characterised in that all of said jaws ( 20, 21, 22 ) are active and are actuable by pressurised fluid.

This invention relates to an apparatus and a method for facilitating theconnection of pipes, and more particularly, but not exclusively, to apowered drill pipe tong for facilitating the connection of sections orstands of drill pipe.

Drill pipe tongs are commonly used for facilitating the connection ofsections or stands of drill pipe to a pipe string. Typically, the pipestring hangs in a wellbore from a spider in a floor of an oil or gasrig.

A section or stand of drill pipe to be connected to the pipe string isswung in from a drill pipe rack to the well centre above the pipestring. A pipe handling arm may be used to guide the drill pipe to aposition above the pipe string. A stabbing guide may then be used toalign a threaded pin of the drill pipe with a threaded box of the pipestring. A drill pipe tong is then used to tighten the connection to atorque of typically 68,000 Nm (50,000 lb.ft).

The drill pipe tong is also used for disconnecting drill pipe. Thisoperation involves breaking the connection which requires a torquetypically greater than the tightening torque which may typically be inthe order of 110,000 Nm (80,000 lb.ft).

A drill pipe tong generally comprises jaws mounted in a rotary which isrotatably arranged in a housing. The jaws are moveable relative to therotary in a generally radial direction towards and away from an upsetpart of the pipe to be gripped. The upset parts of the pipe aregenerally located above the pin and below the box of the pipe and havean enlarged outer diameter and/or a reduced inner diameter.

In use, the rotary is rotated forcing the jaws along cam surfacestowards the upset part of the section of pipe. Once the jaws fullyengage the upset part, the rotary carries on rotating applying torque tothe threads and hence tightens the connection between the section ofpipe and the pipe string.

Several problems have been observed with such prior art drill pipetongs.

In particular, such drill pipe tongs can badly scar the upset part ofthe pipe, particularly if the jaws start rotating relative to the drillpipe.

Once scarred, the pipe is then lowered into the wellbore. Frictionbetween the wellbore (or casing lining the wellbore) and the scarredupset grinds the upset, reducing the diameter.

Scarring of the upset may also be caused by having to reapply the jaws.This is especially common when connecting pipe with “wedge threads”which requires approximately 80° of turn in order to toque theconnection. Many prior art wrenching tongs need to be reapplied to thepipe every 25°.

A reduction in diameter of the upset requires the use of a new drillpipe tong or for the old drill pipe tong to be modified therefor.

An attempt at solving this problem is disclosed in PCT PublicationNumber WO 92/18744, which discloses a rotary comprising hydraulicallyoperated active jaws and stationary passive jaws. The hydraulicallyactivated jaws are engaged fully with the pipe prior to rotation of therotary, thereby substantially reducing scarring. A hydraulic circuit isprovided on the rotary for actuating the jaws. A plunger is used toactivate the hydraulic system by depressing a hydraulic piston of thehydraulic circuit repeatedly. This operation takes time, If severalseconds can be saved per connection, the overall cost of theconstruction of an oil or gas well can be drastically reduced, as longas reliability is not sacrificed. Another problem associated with therotary disclosed in PCT Publication Number WO 92/18744 is that repeateddepressing of the plunger for engaging the jaws fully with the pipe mayitself cause some scaring.

The present invention provides an apparatus for facilitating theconnection of pipes which apparatus comprises a rotary and jaws,characterised in that all of said jaws are active and are actuable bypressurised fluid.

Other aspects of the invention are set out in claims 2 to 14.

There is also provided a method for facilitating the connection ofpipes, the method comprising the steps of actuating the jaws of anapparatus in accordance with the present invention with pressurisedfluid so that the jaws engage with a pipe at a central axis of therotary thereof, rotating said pipe to a predetermined torque, anddisengaging said jaws, preferably with said pressurised fluid.

For a better understanding of the invention, reference will now be made,by way of example, to the accompanying drawings, in which:

FIG. 1 is a top plan view of a rotary of a drill pipe tong in accordancewith the invention with parts shown in cross-section; and

FIG. 2 is a schematic of a part hydraulic, part pneumatic circuit usedin the rotary of FIG. 1.

Referring to FIG. 1 there is shown a rotary which is generallyidentified by reference numeral 1.

The rotary 1 comprises a rigid housing 2 which is provided with atoothed ring 3 for engagement with toothed drive wheels in a stator ofthe drill pipe tong (not shown). The housing 2 is also provided with anopening 4 for receiving a drill pipe.

Three piston and cylinders 5, 6 and 7 are arranged about the rotary 1spaced at 120° to each other and are directed to the centre of therotary 1. The piston and cylinders 5, 6 and 7 comprise static pistons 8,9 and 10 each provided with a piston head 11, 12 and 13. Cylinders 14,15 and 16 are slidable along said piston heads 11, 12 and 13 towards andaway from the centre of the rotary 1. Sealing rings 17, 18 and 19 areprovided in the piston heads 11, 12 and 13 between the piston heads 11,12 and 13 and the cylinders 14, 15 and 16.

Cylinders 14, 15 and 16 are provided with jaws 20, 21 and 22 forengaging with the upset of a drill pipe. The jaws 20 and 21 are locatedin corresponding dovetail slots 23 and 24. The cylinder 16 is shownprovided with an extension member 25 between the cylinder 16 and thejaws 22. The extension member 25 is located in dovetail slots 26 and thegripping elements 22 are located in corresponding dovetail slots 27 inthe extension member 25. In use, either all of the cylinders 14, 15 and16 are provided with extension members 25 or none of the cylinders 14,15 and 16 are provided with extension members 25.

Hydraulic lines 28, 29 and 30 and hydraulic lines 31, 32 and 33 arearranged in each piston 8, 9 and 10 for the provision of hydraulic fluidin front of and behind the piston heads 11, 12 and 13.

A quick release pneumatic fluid supply connection 38, an accumulatorswitch 39 and two release switches 40 and 41 are arranged on the housing2.

The quick release pneumatic fluid supply connection 38 is slidablyarranged in a slot 42 in the housing 2. The slot 42 is shaped to beconcentric with the perimeter of the rotary 1. This allows the rotary 1to rotate a few degrees with a pneumatic fluid supply line attached.

The release switches 40 and 41 are arranged on opposite sides of therotary so that, when release of the gripping elements 20, 21 and 22 fromthe drill pipe is required, at least one will be within easy reach of anoperator. In particular, in use, part of the stator of the drill pipetong (not shown) may obscure use of one of the release switches.

Referring now to FIG. 2 there is shown a circuit which is generallyidentified by reference numeral 100 arranged in and on the housing 2 ofthe rotary 1.

The circuit 100 is provided with a quick release pneumatic fluidconnection 38 slidably arranged in slot 42 of the housing 2 of therotary 1. The pneumatic fluid is supplied from a source 101 via hose102, through a valve 103 and through hose 104 to the connection 38. Thesource supplies pneumatic fluid at approximately 10 bar. A pneumaticline 105 in the housing 2 divides into two branch lines 106 and 107supplying a pneumatic pump 108 and a bellows 109 respectively. Pneumaticline 107 comprises an valve 110 which is biased by spring 111 to an openposition to allow pneumatic fluid to flow to bellows 109.

The circuit 100 is charged while the drill pipe tong is situated awayfrom the drill pipe. This step is carried out by moving the valve 103 toan open position to allow pneumatic fluid to flow from source 101through pneumatic line 105 and by depressing accumulator switch 39. Withthe accumulator switch 39 depressed, branch line 10 is blocked.Pneumatic fluid actuates pneumatic pump 108, which pumps hydraulic fluidaround a sealed circuit 112.

Hydraulic fluid drawn through line 116 and 117 from the bellows 109 ispumped through line 118, through a check valve 120 into an accumulator121. A line 119 leads from the rear of check valve 120 to a rear side ofspring loaded check valve 122. The spring loaded check valve 122 isbiased towards a closed position by a spring 123. A control line 124leads from a rear side of the spring loaded check valve 122, in parallelwith spring 123.

Since accumulator switch 39 is depressed hydraulic fluid is preventedfrom being pumped through line 113 by the valve 114 being in a closedposition.

Hydraulic fluid is prevented from being pumped through a control line124 by release valves 40, 41 which are closed and by a check valve 125.Hydraulic fluid is also prevented from being pumped through control line126 by the check valve 125.

The check valves 120 and 125 inhibit high pressure hydraulic fluidescaping from the accumulator 121.

Control line 126 leads from a front side of the check valve 125 to therear side of a spring loaded check valve 127 in parallel with a spring128 which bias the spring loaded check valve 127 to a closed position.

Pneumatic fluid 129 in the accumulator 121 is compressed by thepneumatic pump 108 to approximately 280 bar. The pump 108 is preventedfrom overloading the accumulator by being designed to stall at 280 baror by use of a pressure relief valve (not shown). The supply ofpneumatic fluid is stopped by closing the valve 103. The accumulatorswitch 39 is now released.

The drill pipe tong can now be offered up to the drill pipe (not shown).The drill pipe is located between the jaws 20, 21 and 22 of the rotary 1through the opening 4.

The jaws 20, 21 and 22 are activated to engage the upset of the drillpipe by opening the valve 103. Pneumatic fluid flows through the valve103, through line 105 into line 106 and drives the pump 108 and alsothrough line 107 to one side of a membrane 130 in bellows 109, squeezinghydraulic fluid to the cylinders 14, 15 and 16 at a high flow rate.Hydraulic fluid pressure acting against spring 128 of the spring loadedcheck valve 127 opens the spring loaded check valve 127. A small amountof hydraulic fluid is allowed to seep from line 126 past the ball of thespring loaded check valve 122 as it opens.

The pump 108 pumps hydraulic fluid into line 113 through valve 114 intoline 131, through a check valve 132 and into the cylinders 14, 15 and 16via branch lines 133, 134 and 135. The pump 108 draws hydraulic fluidfrom the bellows 109 and from behind the piston heads 11, 12 and 13through lines 136, 137 and 138, through device 139, through lines 141,142 into line 140 and through line 143 into line 144 via a flow diverter145, into line 116 into pump 108. The jaws 20, 21 and 22 engage thepipe. The pump 108 will stall or is stopped by removing the pneumaticfluid once the desired engaging force has been reached. This istypically when the pressure in the circuit 100 has built up to 280 bar.

It should be noted that, during this procedure, the accumulator 121 issimultaneously brought up to the same pressure as the engaging pressureif it does not already retain a pressure equal to or higher than theengaging pressure.

The flow diverter 145 is biased to allow fluid communication betweenlines 143 and 144. The device 140 comprises three rotors 146, 147 and148 arranged on a common shaft 149. When hydraulic fluid flows throughthe rotors 146, 147 and 148, the rotors allow equal volumes of fluid topass, thereby ensuring even movement of the jaws 20, 21 and 22 arrangedon the cylinders 14, 15 and 16.

The hose 104 may now be disconnected from the connection 38.

The rotary 1 may now be rotated to rotate the drill pipe to connectdrill pipe.

Once rotation has ceased, the jaws 20, 21 and 22 are disengaged andretracted from the drill pipe. This is carried out by pressing one orboth of the release valves 40, 41. This allows hydraulic fluid to flowfrom the accumulator 121 through control line 124, through spring loadedcheck valve 122 and through release valves 40 and/or 41 into line 115,line 116 and line 117 to bellows 109. A small amount of hydraulic fluidis allowed to seep past the ball of the spring loaded check valve 122.Hydraulic fluid under pressure also flows from control line 126,allowing pressurised hydraulic fluid to flow from infront of the pistonheads 11, 12 and 13 to bellows 109. High pressure hydraulic fluid shiftsflow diverter 145 allowing high pressure hydraulic fluid to flow intoline 143. The flow through line 143 rotates the rotor 147, whichrotatably drives rotors 146 and 148 via shaft 149 and sucks hydraulicfluid out of bellows 109 into the cylinders behind the piston heads 11,12 and 13 and retracts the jaws 20, 21 and 22 in unison. A valve 150 isarranged in parallel with line 143 and bypasses the device 139. Thevalve 150 is biased by a spring 151 to a closed position, however uponthe pressure increasing on the rear side of the piston head 12, thevalve 150 opens equalling the flow rate between the driving rotor 147and the driven rotors 146 and 148.

The hydraulic fluid in front of the piston heads 11, 12 and 13 isexpelled through branch lines 133, 134 and 135 into line 131 a andpasses through spring loaded check valve 128 into line 117 and intobellows 109. The residual hydraulic fluid due to the difference involumes of the cylinders 14, 15 and 16 when engaged and retracted, flowsis stored in the bellows 109. Restrictors 152 and 153 inhibit suddenchanges in pressure upon depression of the release valve 40, 41 and theopening of spring loaded check valve 122.

A safety release valve 155 is provided such that if pressure in theaccumulator 121 needs to be released the safety valve can be operated tovent the hydraulic fluid to atmosphere or into a safety releaseaccumulator 156. The safety release valve may be operated by a controlor be a removable cap in a block 200.

The valves 120, 122, 125, 127, 132, 145, 155 and the respective linesand control lines are arranged in a single block 200. The block 200 maybe formed from any suitable material such as aluminium, aluminium alloyor steel.

It should be noted that the entire circuit 100 is arranged in or/and onthe rotary 1. The pneumatic fluid source 101 is of the type provided onmost drilling rigs and is typically at a pressure of 10 bar.

Various modifications are envisaged to the above apparatus. Inparticular, it is envisaged that a further accumulator could be providedfor providing a charge for moving the jaws into engagement with a pipe.This has the advantage that the pneumatic fluid line may be removed fromthe drill pipe tong before the drill pipe tong is moved about the pipethus saving vital seconds disconnecting the hose from the rotary.

It is also envisaged that the apparatus could be used with thin walledpipe, as it is relatively simple to alter the force applied to the pipeby the jaws.

It is also envisaged that the accumulator could take the form of aspring or a battery

What is claimed is:
 1. An apparatus for facilitating the connection ofpipes which apparatus comprises: a rotary having an open, radiallyextending passageway to facilitate the passage of a pipe into the centreof said rotary; and a set of active jaws, characterized in that saidjaws are actuable by a single pressurization step, and by a device tohelp ensure that said jaws move in unison.
 2. An apparatus as claimed inclaim 1, wherein each of said jaws is mounted on the cylinder of arespective piston and cylinder.
 3. An apparatus as claimed in claim 2,wherein the cylinders of at least two piston and cylinders move towardssaid pipe to engage therewith.
 4. An apparatus as claimed in claim 3,wherein each of said cylinders comprises a curved end to substantiallyconform to said pipe.
 5. An apparatus as claimed in claim 1, whereinsaid jaws further comprising pipe engaging inserts.
 6. An apparatus asclaimed in claim 5, wherein said pipe engaging inserts are angled to benormal to said pipe.
 7. An apparatus as claimed in claim 5, wherein saidpipe engaging inserts are those sold by the applicants under the TradeMark MICRO-GRIP.
 8. An apparatus as claimed in claim 2, furthercomprising extension members for extending the reach of said piston andcylinders.
 9. An apparatus as claimed in claim 2, comprising threepiston and cylinders.
 10. A power tong incorporating an apparatus asclaimed in claim
 1. 11. An apparatus for facilitating the connection oftwo pipes, comprising: a rotary having a radially extending passagewayto facilitate the entry of a pipe; at least two jaws disposed in therotary for contacting the pipe, wherein each of the jaws contacting thepipe are radially movable toward the center of said rotary; a device formoving the at least two jaws in unison; and a rotor for each of the atleast two jaws and a common shaft to which said rotors are fixed. 12.The apparatus of claim 11, wherein each of the at least two jaws aredisposed on a respective piston and cylinder assembly.
 13. The apparatusof claim 12, wherein the cylinders of each of the piston and cylindersassembly move towards said pipe to engage therewith.
 14. The apparatusof claim 13, wherein each of said cylinders comprise a curved end tosubstantially conform to said pipe.
 15. The apparatus of claim 11,wherein the at least two jaws further comprise pipe engaging inserts.16. A method for connecting two tubulars, comprising: placing a firsttubular in an opening of a rotary, the rotary having at least two jawsfor contacting the first tubular; actuating the at least two jaws with asingle pressurization step; contacting the first tubular with the atleast two jaws, wherein each of the jaws contacting the first tubular isradially movable; rotating the first tubular to a predetermined torque;and disengaging the at least two jaws.
 17. The method of claim 16,wherein the at least two jaws are moved in unison.
 18. The method ofclaim 17, wherein the at least two jaws are moved in unison using adevice comprising a rotor for each of the at least two jaws and a commonshaft to which said rotors are fixed.
 19. The method of claim 16,wherein each of the at least two jaws are disposed on a respectivepiston and cylinder assembly.
 20. The method of claim 19, wherein thecylinders of each of the piston and cylinders assembly move towards saidpipe to engage therewith.
 21. An apparatus for facilitating theconnection of pipes which apparatus comprises: a rotary having an open,radially extending passageway to facilitate the passage of a pipe intothe centre of said rotary; and a set of active jaws, characterized inthat said jaws are actuable by a single pressurization step, and by adevice to help ensure that said jaws move in unison, wherein said devicecomprises a rotor for each of said jaws and a common shaft to which saidrotors are fixed.